Alkenoxy groups have been disclosed as substituents on polyphosphazene polymers in U.S. Pat. No. 3,702,833 to Rose et al. The Ross patent shows the preparation of these polyphosphazene copolymers through the reaction of at least two different alkali metal fluoroalkoxides and a small percentage of an alkali metal alkylene alkoxide with a soluble polymer of phosphonitrilic chloride in benzene. Disclosed substitution groups include ##STR3## which are substituted by the reaction of their alkali metal salts with polyphosphonitrilic chloride. While the polymers produced in U.S. Pat. No. 3,702,833 appear to be within the scope of the present invention the method of preparation of the alkylene alkoxy polyphosphazene as set forth in U.S. Pat. No. 3,702,833 using the alkali metal salt substitution procedure produces a polymer having characteristics substantially different than the polymer produced in the present invention. The substitution method used in U.S. Pat. No. 3,702,833 promotes the condensation of aldehydes and ketones and results in the production of a polymer in the form of an undefined tarry mass.
Polyphosphazene polymers containing repeating ##STR4## units in which various substituted and unsubstituted alkoxy, aryloxy, amino and mercapto groups are attached to the phosphorus atom and their method of preparation are described in the prior art as illustrated in the publication "Nitrogen-Phosphorus Compounds", Academic Press, New York, N.Y., 1972 by H. R. Allcock and "Poly(Organophosphazenes)", Chemtech, Sept. 19, 1975 by H. R. Allcock and in such U.S. Pat. Nos. as 3,515,688; 3,702,833, 3,856,712, 3,974,242, and 4,042,561 the disclosures of which are herein incorporated by reference.